Messages in this thread | | | Date | Mon, 18 Sep 2023 22:46:40 +0200 | Subject | Re: [PATCH 4/4] energy_model: use a fixed reference frequency | From | Dietmar Eggemann <> |
| |
On 15/09/2023 15:35, Vincent Guittot wrote: > On Thu, 14 Sept 2023 at 23:07, Dietmar Eggemann > <dietmar.eggemann@arm.com> wrote: >> >> On 01/09/2023 15:03, Vincent Guittot wrote:
[...]
>>> +#ifdef arch_scale_freq_ref >>> +static __always_inline >>> +unsigned long arch_scale_freq_ref_em(int cpu, struct em_perf_domain *pd) >> >> Why is this function named with the arch prefix? >> >> So far we have 5 arch functions (arch_scale_freq_tick() <-> >> arch_scale_freq_ref()) and e.g. Arm/Arm64 defines them with there >> topology_foo implementations. >> >> Isn't arch_scale_freq_ref_em() (as well as arch_scale_freq_ref_policy()) >> different in this sense and so a proper EM function which should >> manifest in its name? > > arch_scale_freq_ref_em() is there to handle cases where > arch_scale_freq_ref() is not defined by arch. I keep arch_ prefix > because this should be provided by architecture which wants to use EM.
That's correct, x86_64 with CONFIG_ENERGY_MODEL=y needs arch_scale_freq_ref_em() returning highest perf_state of the perf_domain. But this function as opposed to arch_scale_freq_ref() does not have to be provided by the arch itself. It's provided by the EM instead. That's why my doubt whether it should be named arch_scale_freq_ref_em().
> In the case of EM, it's only there for allyes|randconfig on arch that > doesn't use arch_topology.c like x86_64
[...]
>>> @@ -241,11 +255,11 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, >>> */ >>> cpu = cpumask_first(to_cpumask(pd->cpus)); >>> scale_cpu = arch_scale_cpu_capacity(cpu); >>> - ps = &pd->table[pd->nr_perf_states - 1]; >>> + ref_freq = arch_scale_freq_ref_em(cpu, pd); >> >> Why not using existing `unsigned long freq` here like in schedutil's >> get_next_freq()? > > Find it easier to read and understand and will not make any difference > in the compiled code
True but I thought it's easier to be able to detect the functional similarity between em_cpu_energy() (*) and get_next_freq().
freq = arch_scale_freq_ref_{policy,em}({policy,(cpu, pd)}); ... (in case of *) freq = map_util_freq(util, freq, max);
Just a nitpick ...
[...]
| |